Just one bit of advice, the area shown in that Instructable gets a lot
of high velocity water. In wet weather it is extremely difficult to
keep your 120volt system totally dry. The usual result is that a GFCI
plug will pop and you are stuck without shore power until the weather
dries out your van. Meanwhile you are making repeated trips in the
pouring rain to reset the GFCI, all to no avail.

So as you are constructing this thing, make sure its waterproof in the
plug area.

-- Gnarlie